This invention relates to dental impression trays, and more particularly for a method and apparatus for molding a dental prosthesis in situ, and also the dental impression trays which can be separated and which can have interchangeable parts.
In repairing dental areas, it is frequently necessary to form a temporary prosthesis for the restoration of defective teeth in a patient's mouth prior to forming the permanent prosthesis. The methods previously used first require the formation of a negative impression in a patient's mouth prior to the preparation of the teeth for receiving the prosthesis. Typically, a positive mold of the teeth is then formed. The teeth are then prepared to receive the prosthesis by cutting them down as is necessary. A second positive mold is then formed of the prepared teeth. Sections of the first positive mold are then cut and properly trimmed and cut down so as to suitably fit in the second positive mold and thereby form the necessary prosthesis on the mold. The necessary dental restorative material is then utilized to form a prosthesis from the positive mold sections. The prosthesis is then replaced in the mouth.
As an improvement over this method, it has been suggested to make a dental prosthesis in situ. In U.S. Pat. No. 3,987,545 there is disclosed the method of forming such a dental prosthesis in situ by first preparing a negative impression of the patient's mouth and from that impression, forming a positive model of the area where tooth restoration is required. An elastomeric mold half is then formed over such positive model. The mold half is formed with overlapping boundaries of the tooth area to be stored in all directions by a predetermined distance. The patient's teeth are then prepared for the restoration including cutting down of selected teeth. The elastomeric mold half is then placed back onto the patient's mouth over the tooth areas prepared for restoration. A vacuum is then caused in the mold cavity formed between the elastomeric mold half and the tooth area, and after the vacuum is achieved, suitable dental restorative material is sent into such mold cavity to form the dental prosthesis in situ.
In order to avoid the necessity of working directly in the patient's mouth, U.S. Pat. No. 4,080,736 provides an additional variation whereby a hard model of the tooth area is formed after it has been prepared for restoration. The previously formed elastomeric mold half is then placed over the hard model outside of the patient's mouth and secured together to form a mold cavity therebetween. The assembly is then placed in a vacuum chamber and suitable dental restorative material is then flowed into the mold cavity to form the dental prosthesis. The prosthesis is then placed into the patient's mouth.
While the formation of the dental prosthesis in situ has been attemped, the various methods and apparatus utilized required numerous steps which caused excessive time and effort until such prosthesis was formed. In all cases, it was first necessary to convert the negative impression of the dental area into a positive model and from the positive model make an elastomeric mold which could then be utilized for the formation of the prosthesis in situ. This procedure itself, in addition to being time consuming, also facilitated errors so that the dental prosthesis formed might not be perfectly fitted and might cause discomfort and injury to the patient.
An additional problem is that the formation of the negative impression utilized a dental impression tray. However, the dental impression tray must be varied in accordance with the sections and configurations of the dental areas. For example, the upper and lower arches of the mouth may vary, and the left and right portions may differ in size. Thus, depending upon the type of impression needed, the depth of the impression tray required will also vary.
When utilizing a standard dental impression tray, it becomes difficult to form the negative dental impression in the portions of the mouth to be restored. Excessive dental impression material is required when utilizing a standard tray for only small areas. Furthermore, in many cases, visability of the area to be restored becomes blocked by means of the large dental impression tray when it is not suitably restricted for the particular area to be restored.
Accordingly, there is need for improvement in the formation of a dental prosthesis in situ. There is also a need for a suitable dental impression tray which can be varied so as to permit modification of the tray for specific utilization in connection with particular sections and configurations of the dental area to be restored.